X for a line 

Mostly seen on snapchat, people generally put it on their stories, meaning that if someone replies to their story with an ‘x’, then the person will reply with a line about what they think of that person.
It’s basically the same thing as x for rate

girl: ‘x for a line’
boy: ‘x’ (probably w/ a pic of himself)
girl: nice boy, should talk more...

X for a line by Steviewonderifhesblind December 17, 2018

x for a line 

Usually on snapchat, usually female. She'll give you a kiss and sexual favours for a line of coke

X for a line...

x for a line by JiggyRabbit November 20, 2018